The present invention relates to clustered file systems utilizing cache storage, and more particularly, to parallel I/O read processing in clustered file systems having cache storage.
In a clustered file system which utilizes cache storage, such as IBM's Panache, due to local and network resource restrictions, a dedicated link between a home site and a cache site for a particular fileset may become overloaded. Typical network load balancing solutions will not directly work due to file level dependency and consistency requirements of the clustered file system, and thus other, less heavily-burdened links are not, allowed to be used to alleviate the burden on an overloaded link. One possible solution to this problem is to split-up a fileset into two or more child filesets, where each link is given one child fileset to manage. However, it is not possible to utilize the links in such a manner because of an inter-file dependency requirement of clustered file systems. In addition, the link may be overloaded due to heavy traffic corresponding to a single large file, e.g., a large database file of greater than one terabyte. It is not possible to split a single file due to data consistency requirements of clustered file systems (and other file systems).
Another issue is dynamics of file workload may change, thus assigning a first fileset's traffic from a first link to a second link may cause the second link to suffer from being overburdened with the first fileset's traffic when it has heavy application I/Os of its own. Therefore, the challenge is to utilize the first link between the home cite and the cache site for a second fileset's traffic while ensuring, across-file and inter-file level consistency and dependency requirements given the limited resources at each gateway node and without affecting the first fileset's traffic. Currently, this causes wastage of network resources, it increases the time required for the home site to be synchronized with the cache site, and results in application latencies and performance degradation.